The present invention relates generally to a process for using heat taken up at a low temperature, which heat is delivered at higher temperature to a heat receiver, through the intermediary of a multi-stage absorption heat pump.
A process of this type is known from Ger. OS No. 2743488. In the known process, solar energy is utilized for space heating. Heat is taken up from the solar collector by a cooling medium which is evaporated in the solar collector. The cooling medium, which comprises a weak solution of two working substances, is transported to a first absorber which operates with a strong solution, and the absorption heat produced in said first absorber is passed to a heating circulation loop. In the known process, the weak solution of the two working substances used to pick up the low temperature heat is passed through the solar collector, and the cooling medium which is evaporated there, (which comprises the strong solution of the two working materials), is passed into the absorber. For regeneration of the weak solution passed to the solar collector and the strong solution passed to the absorber, several separator and reabsorber stages are necessary, as well as pumps to pass the weak solution to the solar collector and to pass the strong solution of the two working substances to the absorber.
The known process has the disadvantage that the two working substances, for example, water as the cooling medium and aqueous lithium bromide as the liquid absorption material, are both passed to the collector. This occasions relatively high material costs for the collector, the feed and the removal pipes, and the pumps and valves--all of which come into contact with the two working substances.
The underlying problem of the present invention is to devise a process for use of heat taken up at relatively low temperature which avoids the disadvantages of known processes, which is more economical and reliable than the known processes, and which can be carried out with equipment which is simply designed and can be reduced at low cost, and which equipment furthermore is not very noisy in operation.
This problem is solved according to the invention, whereby a flow of each transfer medium, for example water or oil,
(a) is passed through a low temperature heat source and absorbs heat there;
(b) then passes through multiple sequential stages of the absorption heat pump, which successively increase in temperature, whereby the flow picks up absorption heat and is heated up to the temperature needed by the heat receiver; whereafter
(c) the flow releases heat to the heat receiver; and
(d) then passes through multiple sequential degassing stages of the absorption heat pump which are coordinated with the absorber stages, whereby it releases evaporation heat and is cooled to a suitable temperature for use in the low temperature heat source.
This process can be carried out as long as the return flow of the heat transfer liquid from the heat receiver evaporates the cooling medium in the degassing stages. It is proposed, in a preferred embodiment of the invention, to regenerate the weak solution of the two working substances in the degassing stages and to regenerate the strong solution of the two working substances in the absorber stages. It is furthermore preferred that a heat transfer medium stream which is heated, e.g., by a gas or oil burner, first be passed through the absorber stages which are working as separators. In this way, the cooling medium may be driven off from the strong solution and then condensed in the degassing stages (which are associated with the respective absorber stages and which operate as resorbers), with the condensation being accompanied by the liberation of heat, and whereby the cooling medium may be absorbed by the weak solution.
Furthermore, the heat transfer medium flow which is cooled in this manner is preferably passed to a heat receiver, with the return flow of the heat transfer medium then passing through the degassing stages (which are operating as resorbers) whereby the flow absorbs the condensation heat and becomes heated up to the initial temperature. Such a regeneration of the weak solution and the strong solution of the pair of working substances is preferably continued until the two working substances reach their original lower concentrations in the degassing stages and their original higher concentrations in the absorber stages.
The inventive process can be applied to great advantage if, for example, high-grade heat energy is available for short and irregular periods of time. If an arrangement is available for the use of, for example, solar energy, geothermal energy, or other low temperature heat, as well as sometimes also high-grade energy, for example, exhaust gas heat, then the arrangement can be switched over with no pause or delay. Thereby, during the periods in which the high-grade energy is available, the pair of working substances are regenerated in the degassing and absorber stages.
The present inventive process has the advantage that each set of associated degassing and absorber stages can be set up in advance as an absorption unit which is completely closed to the outside. With an absorption heat pump operating according to the inventive process, the degasser and absorber are divided into multiple associated degassing and absorber stages, each adjusted to particular evaporation temperatures associated with the given stage, and having a common vapor space. Each degassing stage and its associated absorber stage are part of a hermetically sealed chamber filled with a pair of working substances, and set at a desired pressure. The chamber walls of the degassing stages are disposed within a first flow conduit for a heat transfer medium, with the chamber walls of the absorber stages being disposed in a second flow conduit which is separate from the first. The heat transfer medium flow coming from the source of low temperature takes up absorption heat, by flowing around or through the individual absorber stages, while the return flow of the heat transfer medium flows through the individual adsorption stages in the opposite direction and releases heat to the degassing stages, until the heat transfer medium has been cooled to a temperature in which it is in condition to pick up heat again in the low temperature heat source (which is, for example, a solar collector).